The following relates generally to optical components used in optical communication networks, and, more specifically, to an optical device that can arbitrarily segregate wavelengths into two groups being sent to two separate network nodes.
Optical communication networks are built by combining sub-systems, modules, or components which perform specific functions, including the function of selecting or removing a particular wavelength or group of wavelengths. Briefly, multiple optical signals can be transmitted simultaneously by encoding them in separate carrier wavelengths similar to the way radio stations use different carrier frequencies to which the end user tunes. Encoding multiple signals using different carrier wavelengths is referred to as Dense Wavelength Division Multiplexing (DWDM). A general description of optical networking functions and applications can be found in “Introduction to DWDM Technology”, by S. Kartalopoulos, Wiley-Interscience, 2000.
DWDM Technology has been widely deployed in long haul communications networks. Recently, this technology started migrating to short-haul optical communications networks such as Digital TV delivery, Fiber-to-the-home (FTTH), Internet access, Local Area Networks, back-haul connections for cellular base stations, Wi-Fi hotspots, and other forms of broadband access. At various locations or nodes of an optical network, it is desirable and necessary to split or segregate the wavelengths being carried on a fiber, onto two arbitrary groups, with one group being “dropped” to local equipment, and the other group being passed to another node of the network.
Two-port tunable optical filters of the prior art are suitable for selecting a single wavelength, or a band of contiguous wavelengths, to be dropped from a multiple-wavelength fiber. However, with two-port tunable optical filters, the unselected wavelengths are essentially discarded, and so additional optical components, such as optical splitters and wavelength blockers, must be incorporated to handle the wavelengths that are not being selected or dropped, i.e., the “express” traffic that is being sent to another node of the network. Furthermore, two-port tunable optical filters of the prior art are designed to select a single wavelength or contiguous band or range of wavelengths, and are not able to select any arbitrary set or group of wavelengths.
Modern optical networks make use of Reconfigurable Optical Add/Drop Modules (ROADMs), that are designed to drop and add wavelengths at optical network nodes, while passing on the express traffic to other nodes of the network. Ideally, a ROADM will allow the dropping of any arbitrary subset of wavelengths (up to the number of available drop ports), while passing on all of the unselected wavelengths. As such, three-port wavelength splitter, that is capable of splitting the wavelengths on a fiber into two arbitrary groups of wavelengths, provides enhanced functionality that is highly desirable for use in modern reconfigurable optical networks, as a key element of a ROADM-based network architecture.